/*
 * Copyright (c) 2017 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */


#include <string.h>
#include <stdint.h>
#include <sys/errno.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <dirent.h>
#include <fcntl.h>
#include <libc_private.h>
#include <TargetConditionals.h>
#include <_simple.h>
#include <mach-o/dyld_priv.h>
#include <mach-o/dyld_images.h>
#include <crt_externs.h> // FIXME: Remove once we move off of _NSGetMainExecutable()
#include <os/once_private.h>

#include <array>
#include <algorithm>

#include "dlfcn.h"

#include "AllImages.h"
#include "Loading.h"
#include "Logging.h"
#include "Diagnostics.h"
#include "DyldSharedCache.h"
#include "PathOverrides.h"
#include "APIs.h"
#include "Closure.h"
#include "MachOLoaded.h"
#include "ClosureBuilder.h"
#include "ClosureFileSystemPhysical.h"

#include <dyld/VersionMap.h>

#if __has_feature(ptrauth_calls)
#include <ptrauth.h>
#endif

extern mach_header __dso_handle;

namespace dyld {
    extern dyld_all_image_infos dyld_all_image_infos;
}


namespace dyld3 {


static const void *stripPointer(const void *ptr) {
#if __has_feature(ptrauth_calls)
    return __builtin_ptrauth_strip(ptr, ptrauth_key_asia);
#else
    return ptr;
#endif
}

pthread_mutex_t RecursiveAutoLock::_sMutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;

uint32_t _dyld_image_count(void)
{
    log_apis("_dyld_image_count()\n");

    return gAllImages.count();
}

const mach_header* _dyld_get_image_header(uint32_t imageIndex)
{
    log_apis("_dyld_get_image_header(%d)\n", imageIndex);
    return gAllImages.imageLoadAddressByIndex(imageIndex);
}

intptr_t _dyld_get_image_slide(const mach_header* mh)
{
    log_apis("_dyld_get_image_slide(%p)\n", mh);

    const MachOLoaded* mf = (MachOLoaded*)mh;
    if ( !mf->hasMachOMagic() )
        return 0;

    return mf->getSlide();
}

intptr_t _dyld_get_image_vmaddr_slide(uint32_t imageIndex)
{
    log_apis("_dyld_get_image_vmaddr_slide(%d)\n", imageIndex);

    const mach_header* mh = gAllImages.imageLoadAddressByIndex(imageIndex);
    if ( mh != nullptr )
        return dyld3::_dyld_get_image_slide(mh);
    return 0;
}

const char* _dyld_get_image_name(uint32_t imageIndex)
{
    log_apis("_dyld_get_image_name(%d)\n", imageIndex);
    return gAllImages.imagePathByIndex(imageIndex);
}

const struct mach_header * _dyld_get_prog_image_header()
{
    log_apis("_dyld_get_prog_image_header()\n");
    return gAllImages.mainExecutable();
}

static bool nameMatch(const char* installName, const char* libraryName)
{
    const char* leafName = strrchr(installName, '/');
    if ( leafName == NULL )
        leafName = installName;
    else
        leafName++;

    // -framework case is exact match of leaf name
    if ( strcmp(leafName, libraryName) == 0 )
        return true;

    // -lxxx case: leafName must match "lib" <libraryName> ["." ?] ".dylib"
    size_t leafNameLen = strlen(leafName);
    size_t libraryNameLen = strlen(libraryName);
    if ( leafNameLen < (libraryNameLen+9) )
        return false;
    if ( strncmp(leafName, "lib", 3) != 0 )
        return false;
    if ( strcmp(&leafName[leafNameLen-6], ".dylib") != 0 )
        return false;
    if ( strncmp(&leafName[3], libraryName, libraryNameLen) != 0 )
        return false;
    return (leafName[libraryNameLen+3] == '.');
}


//
// BETTER, USE: dyld_get_program_sdk_version()
//
// Scans the main executable and returns the version of the specified dylib the program was built against.
//
// The library to find is the leaf name that would have been passed to linker tool
// (e.g. -lfoo or -framework foo would use "foo").
//
// Returns -1 if the main executable did not link against the specified library, or is malformed.
//
int32_t NSVersionOfLinkTimeLibrary(const char* libraryName)
{
    log_apis("NSVersionOfLinkTimeLibrary(\"%s\")\n", libraryName);

    __block int32_t result = -1;
    gAllImages.mainExecutable()->forEachDependentDylib(^(const char* loadPath, bool, bool, bool, uint32_t compatVersion, uint32_t currentVersion, bool& stop) {
        if ( nameMatch(loadPath, libraryName) )
            result = currentVersion;
    });
    log_apis("   NSVersionOfLinkTimeLibrary() => 0x%08X\n", result);
    return result;
}


//
// Searches loaded images for the requested dylib and returns its current version.
//
// The library to find is the leaf name that would have been passed to linker tool
// (e.g. -lfoo or -framework foo would use "foo").
//
// If the specified library is not loaded, -1 is returned.
//
int32_t NSVersionOfRunTimeLibrary(const char* libraryName)
{
    log_apis("NSVersionOfRunTimeLibrary(\"%s\")\n", libraryName);
    __block int32_t result = -1;
    gAllImages.forEachImage(^(const dyld3::LoadedImage& loadedImage, bool &stop) {
        const char* installName;
        uint32_t currentVersion;
        uint32_t compatVersion;
        if ( loadedImage.loadedAddress()->getDylibInstallName(&installName, &compatVersion, &currentVersion) && nameMatch(installName, libraryName) ) {
            result = currentVersion;
            stop = true;
        }
    });
    log_apis("   NSVersionOfRunTimeLibrary() => 0x%08X\n", result);
    return result;
}


uint32_t dyld_get_program_sdk_watch_os_version()
{
    log_apis("dyld_get_program_sdk_watch_os_version()\n");

    __block uint32_t retval = 0;
    __block bool versionFound = false;
    dyld3::dyld_get_image_versions(gAllImages.mainExecutable(), ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (versionFound) return;

        if (dyld_get_base_platform(platform) == PLATFORM_WATCHOS) {
            versionFound = true;
            retval = sdk_version;
        }
    });

    return retval;
}

uint32_t dyld_get_program_min_watch_os_version()
{
    log_apis("dyld_get_program_min_watch_os_version()\n");

    __block uint32_t retval = 0;
    __block bool versionFound = false;
    dyld3::dyld_get_image_versions(gAllImages.mainExecutable(), ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (versionFound) return;

        if (dyld_get_base_platform(platform) == PLATFORM_WATCHOS) {
            versionFound = true;
            retval = min_version;
        }
    });

    return retval;
}

uint32_t dyld_get_program_sdk_bridge_os_version()
{
   log_apis("dyld_get_program_sdk_bridge_os_version()\n");

    __block uint32_t retval = 0;
    __block bool versionFound = false;
    dyld3::dyld_get_image_versions(gAllImages.mainExecutable(), ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (versionFound) return;

        if (dyld_get_base_platform(platform) == PLATFORM_BRIDGEOS) {
            versionFound = true;
            retval = sdk_version;
        }
    });

    return retval;
}

uint32_t dyld_get_program_min_bridge_os_version()
{
    log_apis("dyld_get_program_min_bridge_os_version()\n");

    __block uint32_t retval = 0;
    __block bool versionFound = false;
    dyld3::dyld_get_image_versions(gAllImages.mainExecutable(), ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (versionFound) return;

        if (dyld_get_base_platform(platform) == PLATFORM_BRIDGEOS) {
            versionFound = true;
            retval = min_version;
        }
    });

    return retval;
 }

//
// Returns the sdk version (encode as nibble XXXX.YY.ZZ) that the
// specified binary was built against.
//
// First looks for LC_VERSION_MIN_* in binary and if sdk field is
// not zero, return that value.
// Otherwise, looks for the libSystem.B.dylib the binary linked
// against and uses a table to convert that to an sdk version.
//
uint32_t dyld_get_sdk_version(const mach_header* mh)
{
    log_apis("dyld_get_sdk_version(%p)\n", mh);
    __block bool versionFound = false;
    __block uint32_t retval = 0;
    dyld3::dyld_get_image_versions(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (versionFound) return;

        if (platform == ::dyld_get_active_platform()) {
            versionFound = true;
            switch (dyld3::dyld_get_base_platform(platform)) {
                case PLATFORM_BRIDGEOS: retval = sdk_version + 0x00090000; return;
                case PLATFORM_WATCHOS:  retval = sdk_version + 0x00070000; return;
                default: retval = sdk_version; return;
            }
        }
    });

    return retval;
}

uint32_t dyld_get_program_sdk_version()
{
	log_apis("dyld_get_program_sdk_version()\n");
    uint32_t result = dyld3::dyld_get_sdk_version(gAllImages.mainExecutable());
#if TARGET_OS_OSX
    // HACK: We didn't have time to fix all the zippered clients in the spring releases, so keep the mapping. We have resolved it for all new clients using the platform aware SPIs. Since we are doing to deprecate this SPI we will leave the hack in.
    if (dyld_get_active_platform() == (dyld_platform_t)dyld3::Platform::iOSMac) {
        if (result >= 0x000D0400) {
            result = 0x000A0F04;
        } else {
            result = 0x000A0F00;
        }
    }
#endif
    return result;
}

uint32_t dyld_get_min_os_version(const mach_header* mh)
{
    log_apis("dyld_get_min_os_version(%p)\n", mh);
    __block bool versionFound = false;
    __block uint32_t retval = 0;
    dyld3::dyld_get_image_versions(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (versionFound) return;

        if (platform == ::dyld_get_active_platform()) {
            versionFound = true;
            switch (dyld3::dyld_get_base_platform(platform)) {
                case PLATFORM_BRIDGEOS: retval = min_version + 0x00090000; return;
                case PLATFORM_WATCHOS:  retval = min_version + 0x00070000; return;
                default: retval = min_version; return;
            }
        }
    });

    return retval;
}

dyld_platform_t dyld_get_active_platform(void) {
    return gAllImages.platform();
}

dyld_platform_t dyld_get_base_platform(dyld_platform_t platform) {
    switch (platform) {
        case PLATFORM_MACCATALYST:               return PLATFORM_IOS;
        case PLATFORM_IOSSIMULATOR:         return PLATFORM_IOS;
        case PLATFORM_WATCHOSSIMULATOR:     return PLATFORM_WATCHOS;
        case PLATFORM_TVOSSIMULATOR:        return PLATFORM_TVOS;
        default:                            return platform;
    }
}

bool dyld_is_simulator_platform(dyld_platform_t platform) {
    switch(platform) {
        case PLATFORM_IOSSIMULATOR:
        case PLATFORM_WATCHOSSIMULATOR:
        case PLATFORM_TVOSSIMULATOR:
            return true;
        default:
            return false;
    }
}

static
dyld_build_version_t mapFromVersionSet(dyld_build_version_t version) {
    if (version.platform != 0xffffffff) return version;
    auto i = std::lower_bound(sVersionMap.begin(), sVersionMap.end(), version.version);
    assert(i != sVersionMap.end());
    switch(dyld3::dyld_get_base_platform(::dyld_get_active_platform())) {
        case PLATFORM_MACOS: return { .platform = PLATFORM_MACOS, .version = i->macos };
        case PLATFORM_IOS: return { .platform = PLATFORM_IOS, .version = i->ios };
        case PLATFORM_WATCHOS: return { .platform = PLATFORM_WATCHOS, .version = i->watchos };
        case PLATFORM_TVOS: return { .platform = PLATFORM_TVOS, .version = i->tvos };
        case PLATFORM_BRIDGEOS: return { .platform = PLATFORM_BRIDGEOS, .version = i->bridgeos };
        default: return { .platform = 0, .version = 0 };
    }
}

bool dyld_sdk_at_least(const struct mach_header* mh, dyld_build_version_t version) {
    __block bool retval = false;
    version = mapFromVersionSet(version);
    dyld3::dyld_get_image_versions(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (dyld3::dyld_get_base_platform(platform) == version.platform && sdk_version >= version.version) {
            retval = true;
        }
    });
    return retval;
}

bool dyld_minos_at_least(const struct mach_header* mh, dyld_build_version_t version) {
    __block bool retval = false;
    version = mapFromVersionSet(version);
    dyld3::dyld_get_image_versions(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
        if (dyld3::dyld_get_base_platform(platform) == version.platform && min_version >= version.version) {
            retval = true;
        }
    });
    return retval;
}

#if TARGET_OS_OSX
static
uint32_t linkedDylibVersion(const mach_header* mh, const char *installname) {
    __block uint32_t retval = 0;
    ((MachOLoaded*)mh)->forEachDependentDylib(^(const char* loadPath, bool, bool, bool, uint32_t compatVersion, uint32_t currentVersion, bool& stop) {
        if (strcmp(loadPath, installname) == 0) {
            retval = currentVersion;
            stop = true;
        }
    });
    return retval;
}
#endif


#define PACKED_VERSION(major, minor, tiny) ((((major) & 0xffff) << 16) | (((minor) & 0xff) << 8) | ((tiny) & 0xff))

static uint32_t deriveVersionFromDylibs(const struct mach_header* mh) {
#if TARGET_OS_IOS
    // 7.0 is the last version that was in iOSes mapping table, and it is the earliest version that support 64 bit binarie.
    // Since we dropped 32 bit support, we know any binary with a version must be from 7.0
    return 0x00070000;
#elif TARGET_OS_OSX
    // This is a binary without a version load command, we need to infer things
    struct DylibToOSMapping {
        uint32_t dylibVersion;
        uint32_t osVersion;
    };
    uint32_t linkedVersion = linkedDylibVersion(mh, "/usr/lib/libSystem.B.dylib");
    static const DylibToOSMapping versionMapping[] = {
        { PACKED_VERSION(123,0,0),  0x000A0600 },
        { PACKED_VERSION(159,0,0),  0x000A0700 },
        { PACKED_VERSION(169,3,0),  0x000A0800 },
        { PACKED_VERSION(1197,0,0), 0x000A0900 },
        { PACKED_VERSION(0,0,0),    0x000A0900 }
        // We don't need to expand this table because all recent
        // binaries have LC_VERSION_MIN_ load command.
    };
    if ( linkedVersion != 0 ) {
        uint32_t lastOsVersion = 0;
        for (const DylibToOSMapping* p=versionMapping; ; ++p) {
            if ( p->dylibVersion == 0 ) {
                return p->osVersion;
            }
            if ( linkedVersion < p->dylibVersion ) {
                return lastOsVersion;
            }
            lastOsVersion = p->osVersion;
        }
    }
#endif
    return 0;
}

// assumes mh has already been validated
static void dyld_get_image_versions_internal(const struct mach_header* mh, void (^callback)(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version))
{
    const MachOFile* mf = (MachOFile*)mh;
    __block bool lcFound = false;
    mf->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
        lcFound = true;
        // If SDK field is empty then derive the value from library linkages
        if (sdk == 0) {
            sdk = deriveVersionFromDylibs(mh);
        }
        callback((const dyld_platform_t)platform, sdk, minOS);
    });

    // No load command was found, so again, fallback to deriving it from library linkages
    if (!lcFound) {
#if TARGET_OS_IOS
#if __x86_64__ || __x86__
        dyld_platform_t platform = PLATFORM_IOSSIMULATOR;
#else
        dyld_platform_t platform = PLATFORM_IOS;
#endif
#elif TARGET_OS_OSX
        dyld_platform_t platform = PLATFORM_MACOS;
#else
        dyld_platform_t platform = 0;
#endif
        uint32_t derivedVersion = deriveVersionFromDylibs(mh);
        if ( platform != 0 && derivedVersion != 0 ) {
            callback(platform, derivedVersion, 0);
        }
    }
}

void dyld_get_image_versions(const struct mach_header* mh, void (^callback)(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version))
{
    Diagnostics diag;
    const MachOFile* mf = (MachOFile*)mh;
    static dyld_platform_t mainExecutablePlatform = 0;
    static uint32_t mainExecutableSDKVersion = 0;
    static uint32_t mainExecutableMinOSVersion = 0;

    // FIXME: Once dyld2 is gone gAllImages.mainExecutable() will be valid in all cases
    // and we can stop calling _NSGetMachExecuteHeader()
    if (mh == (const struct mach_header*)_NSGetMachExecuteHeader()) {
        if (mainExecutablePlatform) {
            return callback(mainExecutablePlatform, mainExecutableSDKVersion, mainExecutableMinOSVersion);
        }
        mainExecutablePlatform = ::dyld_get_active_platform();
        dyld_get_image_versions_internal(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
            if (platform == PLATFORM_MACOS && dyld_get_base_platform(mainExecutablePlatform) == PLATFORM_IOS) {
                // We are running with DYLD_FORCE_PLATFORM, use the current OSes values
                dyld_get_image_versions_internal(&__dso_handle, ^(dyld_platform_t dyld_platform, uint32_t dyld_sdk_version, uint32_t dyld_min_version) {
                    if (dyld_get_base_platform(dyld_platform) == PLATFORM_IOS) {
                        mainExecutableSDKVersion = dyld_sdk_version;
                        mainExecutableMinOSVersion = dyld_min_version;
                    }
                });
            } else {
                 mainExecutableSDKVersion = sdk_version;
                 mainExecutableMinOSVersion = min_version;
             }
        });
        return callback(mainExecutablePlatform, mainExecutableSDKVersion, mainExecutableMinOSVersion);
    }
#if TARGET_OS_EMBEDDED
    // If we are on embedded AND in the shared cache then the versions should be the same as libdyld
    if (mf->inDyldCache()) {
        static dyld_platform_t libDyldPlatform = 0;
        static uint32_t libDyldSDKVersion = 0;
        static uint32_t libDyldMinOSVersion = 0;
        if (libDyldPlatform == 0) {
            dyld_get_image_versions_internal(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
                libDyldPlatform = platform;
                libDyldSDKVersion = sdk_version;
                libDyldMinOSVersion = min_version;
                //FIXME: Assert if more than one command?
            });
        }
        return callback(libDyldPlatform, libDyldSDKVersion, libDyldMinOSVersion);
    }
#endif
    if ( mf->isMachO(diag, mh->sizeofcmds + sizeof(mach_header_64)) )
        dyld_get_image_versions_internal(mh, callback);
}

struct VIS_HIDDEN VersionSPIDispatcher {
    static bool dyld_program_minos_at_least(dyld_build_version_t version) {
        return dyld_program_minos_at_least_active(version);
    }
    static bool dyld_program_sdk_at_least(dyld_build_version_t version) {
        return dyld_program_sdk_at_least_active(version);
    }
private:
    // We put these into a struct to guarantee so we can control the placement to guarantee a version and the set equivalent
    // Can be loaded via a single load pair instruction.
    struct FastPathData {
        uint32_t version;
        uint32_t versionSetEquivalent;
        dyld_platform_t platform;
    };
    static uint32_t findVersionSetEquuivalent(uint32_t version) {
        uint32_t candidateVersion = 0;
        uint32_t candidateVersionEquivalent = 0;
        uint32_t newVersionSetVersion = 0;
        for (const auto& i : sVersionMap) {
            switch (dyld_get_base_platform(::dyld_get_active_platform())) {
                case PLATFORM_MACOS:    newVersionSetVersion = i.macos; break;
                case PLATFORM_IOS:      newVersionSetVersion = i.ios; break;
                case PLATFORM_WATCHOS:  newVersionSetVersion = i.watchos; break;
                case PLATFORM_TVOS:     newVersionSetVersion = i.tvos; break;
                case PLATFORM_BRIDGEOS: newVersionSetVersion = i.bridgeos; break;
                default: newVersionSetVersion = 0xffffffff; // If we do not know about the platform it is newer than everything
            }
            if (newVersionSetVersion > version) { break; }
            candidateVersion = newVersionSetVersion;
            candidateVersionEquivalent = i.set;
        }
        return candidateVersionEquivalent;
    };

    static void setVersionMappingFastPathData(const struct mach_header* mh) {
        dyld3::dyld_get_image_versions(mh, ^(dyld_platform_t platform, uint32_t sdk_version, uint32_t min_version) {
            minosFastPathData.platform = dyld_get_base_platform(::dyld_get_active_platform());
            sdkFastPathData.platform = dyld_get_base_platform(::dyld_get_active_platform());
            minosFastPathData.version = min_version;
            minosFastPathData.versionSetEquivalent = findVersionSetEquuivalent(min_version);
            sdkFastPathData.version = sdk_version;
            sdkFastPathData.versionSetEquivalent = findVersionSetEquuivalent(sdk_version);
        });
    }

    static void setupFastPath(void) {
        setVersionMappingFastPathData((const struct mach_header*)_NSGetMachExecuteHeader());
        dyld_program_minos_at_least_active = &dyld_program_minos_at_least_fast;
        dyld_program_sdk_at_least_active = &dyld_program_sdk_at_least_fast;
    }

    static bool dyld_program_minos_at_least_slow (dyld_build_version_t version) {
        setupFastPath();
        return dyld_program_minos_at_least_fast(version);
    }

    static bool dyld_program_sdk_at_least_slow (dyld_build_version_t version) {
        setupFastPath();
        return dyld_program_sdk_at_least_fast(version);
    }

    // Fast path implementation of version checks for main executables
    // This works by using the fact that are essentially 3 cases we care about:
    // 1. Comparing the exctuable against any other platform (which should always return false)
    // 2. Comparing the exctuable against a version set (platform 0xfffffff)
    // 3. Comparing the exctuable againstt our base platform
    //
    // We achieve this by setting up a single compare (currentVersion >= version.version) and a couple of
    // of simple tests that will all compile to conditional moves to setup that compare:
    // 1. We setup the comapreVersion as 0. It will only keep that value if it is not a version set and it
    //    it is not the platform we are testing against. 0 will be less than the value encoded in any well
    //    formed binary, so the test will end up returning false
    // 2. If the platform is 0xffffffff it is a version set. In the fast path setup we we calculated a value
    //    that allows a direct comparison, so we set comapreVersion to that (versionSetEquivalent)
    // 3. If it is a concrete platform and it matches the current platform running then we can set comapreVersion
    //    to the actual version number that the was embedded in the binary, which is we stashed in the fast
    //    path data

    static bool dyld_program_minos_at_least_fast (dyld_build_version_t version) {
        uint32_t currentVersion = 0;
        if (version.platform == 0xffffffff) { currentVersion = minosFastPathData.versionSetEquivalent; }
        if (version.platform == minosFastPathData.platform) { currentVersion = minosFastPathData.version; }
        return (currentVersion >= version.version);
    }

    static bool dyld_program_sdk_at_least_fast (dyld_build_version_t version) {
        uint32_t currentVersion = 0;
        if (version.platform == 0xffffffff) { currentVersion = sdkFastPathData.versionSetEquivalent ; }
        if (version.platform == sdkFastPathData.platform) { currentVersion = sdkFastPathData.version; }
        return (currentVersion >= version.version);
    }

    static bool (*dyld_program_minos_at_least_active)(dyld_build_version_t version);
    static bool (*dyld_program_sdk_at_least_active)(dyld_build_version_t version);
    static FastPathData minosFastPathData;
    static FastPathData sdkFastPathData;
};

bool (*VersionSPIDispatcher::dyld_program_minos_at_least_active)(dyld_build_version_t version) = &VersionSPIDispatcher::dyld_program_minos_at_least_slow;
bool (*VersionSPIDispatcher::dyld_program_sdk_at_least_active)(dyld_build_version_t version) = &VersionSPIDispatcher::dyld_program_sdk_at_least_slow;
VersionSPIDispatcher::FastPathData VersionSPIDispatcher::minosFastPathData = {0, 0, 0};
VersionSPIDispatcher::FastPathData VersionSPIDispatcher::sdkFastPathData = {0, 0, 0};


// We handle this directly instead of dispatching through dyld3::dyld_program_sdk_at_least because they are very perf sensitive
bool dyld_program_minos_at_least(dyld_build_version_t version) {
    return VersionSPIDispatcher::dyld_program_minos_at_least(version);
}

bool dyld_program_sdk_at_least(dyld_build_version_t version) {
    return VersionSPIDispatcher::dyld_program_sdk_at_least(version);
}

uint32_t dyld_get_program_min_os_version()
{
    log_apis("dyld_get_program_min_os_version()\n");
    return dyld3::dyld_get_min_os_version(gAllImages.mainExecutable());
}

bool _dyld_get_image_uuid(const mach_header* mh, uuid_t uuid)
{
    log_apis("_dyld_get_image_uuid(%p, %p)\n", mh, uuid);

    const MachOFile* mf = (MachOFile*)mh;
    if ( !mf->hasMachOMagic() )
        return false;

    return mf->getUuid(uuid);
}

//
// _NSGetExecutablePath() copies the path of the main executable into the buffer. The bufsize parameter
// should initially be the size of the buffer.  The function returns 0 if the path was successfully copied,
// and *bufsize is left unchanged. It returns -1 if the buffer is not large enough, and *bufsize is set
// to the size required.
//
int _NSGetExecutablePath(char* buf, uint32_t* bufsize)
{
    log_apis("_NSGetExecutablePath(%p, %p)\n", buf, bufsize);

    const closure::Image* mainImage = gAllImages.mainExecutableImage();
    const char* path = gAllImages.imagePath(mainImage);
    size_t pathSize = strlen(path) + 1;
    if ( *bufsize >= pathSize ) {
        strcpy(buf, path);
        return 0;
    }
    *bufsize = (uint32_t)pathSize;
    return -1;
}

/*
 1: 让gAllImages._loadedImages(主Image和它依赖的库)都执行func函数
 2: 将函数注册到_loadNotifiers数组中
 */
void _dyld_register_func_for_add_image(void (*func)(const mach_header *mh, intptr_t vmaddr_slide)) {
    log_apis("_dyld_register_func_for_add_image(%p)\n", func);

    gAllImages.addLoadNotifier(func);
}

void _dyld_register_func_for_remove_image(void (*func)(const mach_header *mh, intptr_t vmaddr_slide))
{
    log_apis("_dyld_register_func_for_remove_image(%p)\n", func);

    gAllImages.addUnloadNotifier(func);
}

// 注册回调函数
void _dyld_objc_notify_register(_dyld_objc_notify_mapped    mapped,
                                _dyld_objc_notify_init      init,
                                _dyld_objc_notify_unmapped  unmapped) {
    log_apis("_dyld_objc_notify_register(%p, %p, %p)\n", mapped, init, unmapped);

    gAllImages.setObjCNotifiers(mapped, init, unmapped);
}


const mach_header* dyld_image_header_containing_address(const void* addr)
{
    log_apis("dyld_image_header_containing_address(%p)\n", addr);

    addr = stripPointer(addr);

    const MachOLoaded* ml;
    if ( gAllImages.infoForImageMappedAt(addr, &ml, nullptr, nullptr) )
        return ml;

    return nullptr;
}


const char* dyld_image_path_containing_address(const void* addr)
{
    log_apis("dyld_image_path_containing_address(%p)\n", addr);

    addr = stripPointer(addr);
    const char* result = gAllImages.pathForImageMappedAt(addr);

    log_apis("   dyld_image_path_containing_address() => %s\n", result);
    return result;
}

    

bool _dyld_is_memory_immutable(const void* addr, size_t length)
{
    return gAllImages.immutableMemory(addr, length);
}

int dladdr(const void* addr, Dl_info* info)
{
    log_apis("dladdr(%p, %p)\n", addr, info);

    // <rdar://problem/42171466> calling dladdr(xx,NULL) crashes
    if ( info == NULL )
        return 0; // failure

    addr = stripPointer(addr);

    __block int         result = 0;
    const MachOLoaded*  ml     = nullptr;
    const char*         path   = nullptr;
    if ( gAllImages.infoForImageMappedAt(addr, &ml, nullptr, &path) ) {
        info->dli_fname = path;
        info->dli_fbase = (void*)ml;

        uint64_t symbolAddr;
        if ( addr == info->dli_fbase ) {
            // special case lookup of header
            info->dli_sname = "__dso_handle";
            info->dli_saddr = info->dli_fbase;
        }
        else if ( ml->findClosestSymbol((long)addr, &(info->dli_sname), &symbolAddr) ) {
            info->dli_saddr = (void*)(long)symbolAddr;
            // never return the mach_header symbol
            if ( info->dli_saddr == info->dli_fbase ) {
                info->dli_sname = nullptr;
                info->dli_saddr = nullptr;
            }
            // strip off leading underscore
            else if ( (info->dli_sname != nullptr) && (info->dli_sname[0] == '_') ) {
                info->dli_sname = info->dli_sname + 1;
            }
        }
        else {
            info->dli_sname = nullptr;
            info->dli_saddr = nullptr;
        }
        result = 1;
    }

    if ( result == 0 )
        log_apis("   dladdr() => 0\n");
    else
        log_apis("   dladdr() => 1, { \"%s\", %p, \"%s\", %p }\n", info->dli_fname, info->dli_fbase, info->dli_sname, info->dli_saddr);
    return result;
}

#if !TARGET_OS_DRIVERKIT

struct PerThreadErrorMessage
{
    size_t      sizeAllocated;
    bool        valid;
    char        message[1];
};

static void dlerror_perThreadKey_once(void* ctx)
{
    pthread_key_t* dlerrorPThreadKeyPtr = (pthread_key_t*)ctx;
    pthread_key_create(dlerrorPThreadKeyPtr, &free);
}

static pthread_key_t dlerror_perThreadKey()
{
    static os_once_t  onceToken;
    static pthread_key_t    dlerrorPThreadKey;
    os_once(&onceToken, &dlerrorPThreadKey, dlerror_perThreadKey_once);
    return dlerrorPThreadKey;
}

static void clearErrorString()
{
    PerThreadErrorMessage* errorBuffer = (PerThreadErrorMessage*)pthread_getspecific(dlerror_perThreadKey());
    if ( errorBuffer != nullptr )
        errorBuffer->valid = false;
}

__attribute__((format(printf, 1, 2)))
static void setErrorString(const char* format, ...)
{
    _SIMPLE_STRING buf = _simple_salloc();
    if ( buf != nullptr ) {
        va_list    list;
        va_start(list, format);
        _simple_vsprintf(buf, format, list);
        va_end(list);
        size_t strLen = strlen(_simple_string(buf)) + 1;
        size_t sizeNeeded = sizeof(PerThreadErrorMessage) + strLen;
        PerThreadErrorMessage* errorBuffer = (PerThreadErrorMessage*)pthread_getspecific(dlerror_perThreadKey());
        if ( errorBuffer != nullptr ) {
            if ( errorBuffer->sizeAllocated < sizeNeeded ) {
                free(errorBuffer);
                errorBuffer = nullptr;
            }
        }
        if ( errorBuffer == nullptr ) {
            size_t allocSize = std::max(sizeNeeded, (size_t)256);
            PerThreadErrorMessage* p = (PerThreadErrorMessage*)malloc(allocSize);
            p->sizeAllocated = allocSize;
            p->valid = false;
            pthread_setspecific(dlerror_perThreadKey(), p);
            errorBuffer = p;
        }
        strcpy(errorBuffer->message, _simple_string(buf));
        errorBuffer->valid = true;
        _simple_sfree(buf);
    }
}

char* dlerror()
{
    log_apis("dlerror()\n");

    PerThreadErrorMessage* errorBuffer = (PerThreadErrorMessage*)pthread_getspecific(dlerror_perThreadKey());
    if ( errorBuffer != nullptr ) {
        if ( errorBuffer->valid ) {
            // you can only call dlerror() once, then the message is cleared
            errorBuffer->valid = false;
            return errorBuffer->message;
        }
    }
    return nullptr;
}

#if __arm64__
    #define CURRENT_CPU_TYPE CPU_TYPE_ARM64
#elif __arm__
    #define CURRENT_CPU_TYPE CPU_TYPE_ARM
#endif


static void* makeDlHandle(const mach_header* mh, bool dontContinue)
{
    uintptr_t flags = (dontContinue ? 1 : 0);
    return (void*)((((uintptr_t)mh) >> 5) | flags);
}

VIS_HIDDEN
void parseDlHandle(void* h, const MachOLoaded** mh, bool* dontContinue)
{
    *dontContinue = (((uintptr_t)h) & 1);
    *mh           = (const MachOLoaded*)((((uintptr_t)h) & (-2)) << 5);
}

int dlclose(void* handle)
{
    DYLD_LOAD_LOCK_THIS_BLOCK
    log_apis("dlclose(%p)\n", handle);

    // silently accept magic handles for main executable
    if ( handle == RTLD_MAIN_ONLY )
        return 0;
    if ( handle == RTLD_DEFAULT )
        return 0;
    
    const MachOLoaded*  mh;
    bool                dontContinue;
    parseDlHandle(handle, &mh, &dontContinue);

    __block bool unloadable = false;
    __block bool validHandle = false;
    gAllImages.infoForImageMappedAt(mh, ^(const LoadedImage& foundImage, uint8_t permissions) {
        validHandle = true;
        if ( !foundImage.image()->neverUnload() )
            unloadable = true;
    });
    if ( unloadable ) {
        gAllImages.decRefCount(mh);  // removes image if reference count went to zero
    }

    if ( validHandle ) {
        clearErrorString();
        return 0;
    }
    else {
        setErrorString("invalid handle passed to dlclose()");
        return -1;
    }
}


void* dlopen_internal(const char* path, int mode, void* callerAddress)
{    
    DYLD_LOAD_LOCK_THIS_BLOCK
    log_apis("dlopen(\"%s\", 0x%08X)\n", ((path==NULL) ? "NULL" : path), mode);

    clearErrorString();

    // passing NULL for path means return magic object
    if ( path == NULL ) {
        // RTLD_FIRST means any dlsym() calls on the handle should only search that handle and not subsequent images
        if ( (mode & RTLD_FIRST) != 0 )
            return RTLD_MAIN_ONLY;
        else
            return RTLD_DEFAULT;
    }

    const char* leafName = strrchr(path, '/');
    if ( leafName != nullptr )
        ++leafName;
    else
        leafName = path;


#if TARGET_OS_IPHONE
    // <rdar://problem/40235395> dyld3: dlopen() not working with non-canonical paths
    char canonicalPath[PATH_MAX];
    if ( leafName != path ) {
        // make path canonical if it contains a // or ./
        if ( (strstr(path, "//") != NULL) || (strstr(path, "./") != NULL) ) {
            const char* lastSlash = strrchr(path, '/');
            char dirPath[PATH_MAX];
            if ( strlcpy(dirPath, path, sizeof(dirPath)) < sizeof(dirPath) ) {
                dirPath[lastSlash-path] = '\0';
                if ( realpath(dirPath, canonicalPath) ) {
                    strlcat(canonicalPath, "/", sizeof(canonicalPath));
                    if ( strlcat(canonicalPath, lastSlash+1, sizeof(canonicalPath)) < sizeof(canonicalPath) ) {
                        // if all fit in buffer, use new canonical path
                        path = canonicalPath;
                    }
                }
            }
        }
    }
#endif

    // RTLD_FIRST means when dlsym() is called with handle, only search the image and not those loaded after it
    const bool firstOnly = (mode & RTLD_FIRST);

    // RTLD_LOCAL means when flat searches of all images (e.g. RTLD_DEFAULT) is done, this image should be skipped. But dlsym(handle, xx) can find symbols
    const bool rtldLocal = (mode & RTLD_LOCAL);

    // RTLD_NODELETE means don't unmap image during dlclose(). Leave the memory mapped, but orphan (leak) it.
    // Note: this is a weird state and it slightly different semantics that other OSs
    const bool rtldNoDelete = (mode & RTLD_NODELETE);

    // RTLD_NOLOAD means do nothing if image not already loaded
    const bool rtldNoLoad = (mode & RTLD_NOLOAD);

    // RTLD_NOW means force lazy symbols bound and fail dlopen() if some cannot be bound
    const bool rtldNow = (mode & RTLD_NOW);

    // try to load image from specified path
    Diagnostics diag;
    const mach_header* topLoadAddress = gAllImages.dlopen(diag, path, rtldNoLoad, rtldLocal, rtldNoDelete, rtldNow, false, callerAddress);
    if ( diag.hasError() ) {
        setErrorString("dlopen(%s, 0x%04X): %s", path, mode, diag.errorMessage());
        log_apis("   dlopen: closure creation error: %s\n", diag.errorMessage());
        return nullptr;
    }
    if ( topLoadAddress == nullptr ) {
        log_apis("   dlopen(%s) => NULL\n", leafName);
        return nullptr;
    }
    void* result = makeDlHandle(topLoadAddress, firstOnly);
    log_apis("   dlopen(%s) => %p\n", leafName, result);
    return result;

}

bool dlopen_preflight_internal(const char* path)
{
    DYLD_LOAD_LOCK_THIS_BLOCK
    log_apis("dlopen_preflight(%s)\n", path);

    // check if path is in dyld shared cache, or is a symlink to the cache
    if ( _dyld_shared_cache_contains_path(path) )
        return true;

    // check if file is loadable
    Diagnostics diag;
    closure::FileSystemPhysical fileSystem;
    char realerPath[MAXPATHLEN];
    closure::LoadedFileInfo loadedFileInfo = MachOAnalyzer::load(diag, fileSystem, path, gAllImages.archs(), (Platform)gAllImages.platform(), realerPath);
    if ( loadedFileInfo.fileContent != nullptr ) {
        fileSystem.unloadFile(loadedFileInfo);
        return true;
    }

    return false;
}

static void* dlsym_search(const char* symName, const LoadedImage& start, bool searchStartImage, MachOLoaded::DependentToMachOLoaded reExportHelper,
                          bool* resultPointsToInstructions)
{
    MachOLoaded::DependentToMachOLoaded finder = ^(const MachOLoaded* mh, uint32_t depIndex) {
        return gAllImages.findDependent(mh, depIndex);
    };
    //fprintf(stderr, "dlsym_search: %s, start=%s\n", symName, start.image()->path());

    // walk all dependents of 'start' in order looking for symbol
    __block void* result = nullptr;
    gAllImages.visitDependentsTopDown(start, ^(const LoadedImage& aLoadedImage, bool& stop) {
        //fprintf(stderr, "    search: %s\n", aLoadedImage.image()->path());
        if ( !searchStartImage && aLoadedImage.image() == start.image() )
            return;
        if ( aLoadedImage.loadedAddress()->hasExportedSymbol(symName, finder, &result, resultPointsToInstructions) ) {
            result = gAllImages.interposeValue(result);
            stop = true;
        }
    });

    return result;
}


void* dlsym_internal(void* handle, const char* symbolName, void* callerAddress)
{
    log_apis("dlsym(%p, \"%s\")\n", handle, symbolName);

    clearErrorString();

    MachOLoaded::DependentToMachOLoaded finder = ^(const MachOLoaded* mh, uint32_t depIndex) {
        return gAllImages.findDependent(mh, depIndex);
    };

    // dlsym() assumes symbolName passed in is same as in C source code
    // dyld assumes all symbol names have an underscore prefix
    BLOCK_ACCCESSIBLE_ARRAY(char, underscoredName, strlen(symbolName)+2);
    underscoredName[0] = '_';
    strcpy(&underscoredName[1], symbolName);

    __block void* result = nullptr;
    __block bool resultPointsToInstructions = false;
    if ( handle == RTLD_DEFAULT ) {
        // magic "search all in load order" handle
        gAllImages.forEachImage(^(const LoadedImage& loadedImage, bool& stop) {
            if ( loadedImage.hideFromFlatSearch() )
                return;
            if ( loadedImage.loadedAddress()->hasExportedSymbol(underscoredName, finder, &result, &resultPointsToInstructions) ) {
                stop = true;
            }
        });
        if ( result != nullptr ) {
            result = gAllImages.interposeValue(result);
#if __has_feature(ptrauth_calls)
            if (resultPointsToInstructions)
                result = __builtin_ptrauth_sign_unauthenticated(result, ptrauth_key_asia, 0);
#endif
            log_apis("   dlsym() => %p\n", result);
            return result;
        }
        setErrorString("dlsym(RTLD_DEFAULT, %s): symbol not found", symbolName);
        log_apis("   dlsym() => NULL\n");
        return nullptr;
    }
    else if ( handle == RTLD_MAIN_ONLY ) {
        // magic "search only main executable" handle
        if ( gAllImages.mainExecutable()->hasExportedSymbol(underscoredName, finder, &result, &resultPointsToInstructions) ) {
            result = gAllImages.interposeValue(result);
            log_apis("   dlsym() => %p\n", result);
#if __has_feature(ptrauth_calls)
            if (resultPointsToInstructions)
                result = __builtin_ptrauth_sign_unauthenticated(result, ptrauth_key_asia, 0);
#endif
            return result;
        }
        setErrorString("dlsym(RTLD_MAIN_ONLY, %s): symbol not found", symbolName);
        log_apis("   dlsym() => NULL\n");
        return nullptr;
    }
    // rest of cases search in dependency order
    if ( handle == RTLD_NEXT ) {
        // magic "search what I would see" handle
        __block bool foundCaller = false;
        gAllImages.infoForImageMappedAt(callerAddress, ^(const LoadedImage& foundImage, uint8_t permissions) {
            foundCaller = true;
            result = dlsym_search(underscoredName, foundImage, false, finder, &resultPointsToInstructions);
        });
        if ( !foundCaller ) {
            setErrorString("dlsym(RTLD_NEXT, %s): called by unknown image (caller=%p)", symbolName, callerAddress);
            return nullptr;
        }
    }
    else if ( handle == RTLD_SELF ) {
        // magic "search me, then what I would see" handle
        __block bool foundCaller = false;
        gAllImages.infoForImageMappedAt(callerAddress, ^(const LoadedImage& foundImage, uint8_t permissions) {
            foundCaller = true;
            result = dlsym_search(underscoredName, foundImage, true, finder, &resultPointsToInstructions);
        });
        if ( !foundCaller ) {
            setErrorString("dlsym(RTLD_SELF, %s): called by unknown image (caller=%p)", symbolName, callerAddress);
            return nullptr;
        }
    }
    else {
        // handle value was something returned by dlopen()
        const MachOLoaded*  mh;
        bool                dontContinue;
        parseDlHandle(handle, &mh, &dontContinue);

        __block bool foundCaller = false;
        gAllImages.infoForImageWithLoadAddress(mh, ^(const LoadedImage& foundImage) {
            foundCaller = true;
            if ( dontContinue ) {
                // RTLD_FIRST only searches one place
                // we go through infoForImageWithLoadAddress() to validate the handle
                if (mh->hasExportedSymbol(underscoredName, finder, &result, &resultPointsToInstructions))
                    result = gAllImages.interposeValue(result);
            }
            else {
                result = dlsym_search(underscoredName, foundImage, true, finder, &resultPointsToInstructions);
            }
        });
        if ( !foundCaller ) {
            setErrorString("dlsym(%p, %s): invalid handle", handle, symbolName);
            log_apis("   dlsym() => NULL\n");
            return nullptr;
        }
    }

    if ( result != nullptr ) {
#if __has_feature(ptrauth_calls)
        if (resultPointsToInstructions)
            result = __builtin_ptrauth_sign_unauthenticated(result, ptrauth_key_asia, 0);
#endif
        log_apis("   dlsym() => %p\n", result);
        return result;
    }

    setErrorString("dlsym(%p, %s): symbol not found", handle, symbolName);
    log_apis("   dlsym() => NULL\n");
    return nullptr;
}
#endif // !TARGET_OS_DRIVERKIT


const struct dyld_all_image_infos* _dyld_get_all_image_infos()
{
    return gAllImages.oldAllImageInfo();
}

bool dyld_shared_cache_some_image_overridden()
{
    log_apis("dyld_shared_cache_some_image_overridden()\n");

    return gAllImages.hasCacheOverrides();
}

bool _dyld_get_shared_cache_uuid(uuid_t uuid)
{
    log_apis("_dyld_get_shared_cache_uuid()\n");

    const DyldSharedCache* sharedCache = (DyldSharedCache*)gAllImages.cacheLoadAddress();
    if ( sharedCache == nullptr )
        return false;

    if ( gAllImages.oldAllImageInfo() != nullptr ) {
        memcpy(uuid, gAllImages.oldAllImageInfo()->sharedCacheUUID, sizeof(uuid_t));
        return true;
    }
    return false;
}

// 返回共享缓存的地址，并把cache所有map的大小设置给mappedSize
const void* _dyld_get_shared_cache_range(size_t* mappedSize) {
    log_apis("_dyld_get_shared_cache_range()\n");

    const DyldSharedCache* sharedCache = (DyldSharedCache*)gAllImages.cacheLoadAddress();
    if ( sharedCache != nullptr ) {
        // 求出cache所有map的大小
        *mappedSize = (size_t)sharedCache->mappedSize();
        return sharedCache;
    }
    *mappedSize = 0;
    return NULL;
}

bool _dyld_shared_cache_optimized()
{
    const DyldSharedCache* sharedCache = (DyldSharedCache*)gAllImages.cacheLoadAddress();
    if ( sharedCache != nullptr ) {
        return (sharedCache->header.cacheType == kDyldSharedCacheTypeProduction);
    }
    return false;
}

bool _dyld_shared_cache_is_locally_built()
{
    const DyldSharedCache* sharedCache = (DyldSharedCache*)gAllImages.cacheLoadAddress();
    if ( sharedCache != nullptr ) {
        return (sharedCache->header.locallyBuiltCache == 1);
    }
    return false;
}

uint32_t _dyld_launch_mode()
{
    return gAllImages.launchMode();
}


void _dyld_images_for_addresses(unsigned count, const void* addresses[], dyld_image_uuid_offset infos[])
{
    log_apis("_dyld_images_for_addresses(%u, %p, %p)\n", count, addresses, infos);

    // in stack crawls, common for contiguous fames to be in same image, so cache
    // last lookup and check if next addresss in in there before doing full search
    const MachOLoaded*    ml       = nullptr;
    uint64_t              textSize = 0;
    const void*           end      = (void*)ml;
    for (unsigned i=0; i < count; ++i) {
        const void* addr = stripPointer(addresses[i]);
        bzero(&infos[i], sizeof(dyld_image_uuid_offset));
        if ( (ml == nullptr) || (addr < (void*)ml) || (addr > end) ) {
            if ( gAllImages.infoForImageMappedAt(addr, &ml, &textSize, nullptr) ) {
                end = (void*)((uint8_t*)ml + textSize);
            }
            else {
                ml       = nullptr;
                textSize = 0;
            }
        }
        if ( ml != nullptr ) {
            infos[i].image         = ml;
            infos[i].offsetInImage = (uintptr_t)addr - (uintptr_t)ml;
            ml->getUuid(infos[i].uuid);
        }
    }
}

void _dyld_register_for_image_loads(void (*func)(const mach_header* mh, const char* path, bool unloadable))
{
    gAllImages.addLoadNotifier(func);
}

void _dyld_register_for_bulk_image_loads(void (*func)(unsigned imageCount, const struct mach_header* mhs[], const char* paths[]))
{
    gAllImages.addBulkLoadNotifier(func);
}

bool _dyld_find_unwind_sections(void* addr, dyld_unwind_sections* info)
{
    log_apis("_dyld_find_unwind_sections(%p, %p)\n", addr, info);
    addr = (void*)stripPointer(addr);

    const MachOLoaded* ml = nullptr;
    if ( gAllImages.infoForImageMappedAt(addr, &ml, nullptr, nullptr) ) {
        info->mh                            = ml;
        info->dwarf_section                 = nullptr;
        info->dwarf_section_length          = 0;
        info->compact_unwind_section        = nullptr;
        info->compact_unwind_section_length = 0;

        uint64_t size;
        if ( const void* content = ml->findSectionContent("__TEXT", "__eh_frame", size) ) {
            info->dwarf_section                 = content;
            info->dwarf_section_length          = (uintptr_t)size;
        }
        if ( const void* content = ml->findSectionContent("__TEXT", "__unwind_info", size) ) {
            info->compact_unwind_section        = content;
            info->compact_unwind_section_length = (uintptr_t)size;
        }
        return true;
    }

    return false;
}


bool dyld_process_is_restricted()
{
    log_apis("dyld_process_is_restricted()\n");
    return gAllImages.isRestricted();
}


const char* dyld_shared_cache_file_path()
{
    log_apis("dyld_shared_cache_file_path()\n");

    return gAllImages.dyldCachePath();
}


bool dyld_has_inserted_or_interposing_libraries()
{
   log_apis("dyld_has_inserted_or_interposing_libraries()\n");

   return gAllImages.hasInsertedOrInterposingLibraries();
}


void dyld_dynamic_interpose(const mach_header* mh, const dyld_interpose_tuple array[], size_t count)
{
    log_apis("dyld_dynamic_interpose(%p, %p, %lu)\n", mh, array, count);
    // FIXME
}


static void* mapStartOfCache(const char* path, size_t length)
{
    struct stat statbuf;
    if ( dyld3::stat(path, &statbuf) == -1 )
        return NULL;

    if ( statbuf.st_size < length )
        return NULL;

    int cache_fd = dyld3::open(path, O_RDONLY, 0);
    if ( cache_fd < 0 )
        return NULL;

    void* result = ::mmap(NULL, length, PROT_READ, MAP_PRIVATE, cache_fd, 0);
    close(cache_fd);

    if ( result == MAP_FAILED )
        return NULL;

    return result;
}

static const DyldSharedCache* findCacheInDirAndMap(const uuid_t cacheUuid, const char* dirPath, size_t& sizeMapped)
{
    DIR* dirp = ::opendir(dirPath);
    if ( dirp != NULL) {
        dirent entry;
        dirent* entp = NULL;
        char cachePath[PATH_MAX];
        while ( ::readdir_r(dirp, &entry, &entp) == 0 ) {
            if ( entp == NULL )
                break;
            if ( entp->d_type != DT_REG ) 
                continue;
            if ( strlcpy(cachePath, dirPath, PATH_MAX) >= PATH_MAX )
                continue;
            if ( strlcat(cachePath, "/", PATH_MAX) >= PATH_MAX )
                continue;
            if ( strlcat(cachePath, entp->d_name, PATH_MAX) >= PATH_MAX )
                continue;
            if ( const DyldSharedCache* cache = (DyldSharedCache*)mapStartOfCache(cachePath, 0x00100000) ) {
                uuid_t foundUuid;
                cache->getUUID(foundUuid);
                if ( (::memcmp(cache, "dyld_", 5) != 0) || (::memcmp(foundUuid, cacheUuid, 16) != 0) ) {
                    // wrong uuid, unmap and keep looking
                    ::munmap((void*)cache, 0x00100000);
                }
                else {
                    // found cache
                    closedir(dirp);
                    sizeMapped = 0x00100000;
                    return cache;
                }
            }
        }
        closedir(dirp);
    }
    return nullptr;
}

int dyld_shared_cache_find_iterate_text(const uuid_t cacheUuid, const char* extraSearchDirs[], void (^callback)(const dyld_shared_cache_dylib_text_info* info))
{
    log_apis("dyld_shared_cache_find_iterate_text()\n");

    // see if requested cache is the active one in this process
    size_t sizeMapped = 0;
    const DyldSharedCache* sharedCache = (DyldSharedCache*)gAllImages.cacheLoadAddress();
    if ( sharedCache != nullptr ) {
        uuid_t runningUuid;
        sharedCache->getUUID(runningUuid);
        if ( ::memcmp(runningUuid, cacheUuid, 16) != 0 )
            sharedCache = nullptr;
    }
    if ( sharedCache == nullptr ) {
         // if not, look in default location for cache files
    #if TARGET_OS_IPHONE
        sharedCache = findCacheInDirAndMap(cacheUuid, IPHONE_DYLD_SHARED_CACHE_DIR, sizeMapped);
    #else
        sharedCache = findCacheInDirAndMap(cacheUuid, MACOSX_MRM_DYLD_SHARED_CACHE_DIR, sizeMapped);
   #endif
        // if not there, look in extra search locations
        if ( sharedCache == nullptr ) {
            for (const char** p = extraSearchDirs; *p != nullptr; ++p) {
                sharedCache = findCacheInDirAndMap(cacheUuid, *p, sizeMapped);
                if ( sharedCache != nullptr )
                    break;
            }
        }
    }
    if ( sharedCache == nullptr )
        return -1;

    // get base address of cache
    __block uint64_t cacheUnslidBaseAddress = 0;
    sharedCache->forEachRegion(^(const void *content, uint64_t vmAddr, uint64_t size,
                                 uint32_t initProt, uint32_t maxProt, uint64_t flags) {
        if ( cacheUnslidBaseAddress == 0 )
            cacheUnslidBaseAddress = vmAddr;
    });

    // iterate all images
    sharedCache->forEachImageTextSegment(^(uint64_t loadAddressUnslid, uint64_t textSegmentSize, const uuid_t dylibUUID, const char* installName, bool& stop) {
        dyld_shared_cache_dylib_text_info dylibTextInfo;
        dylibTextInfo.version              = 2;
        dylibTextInfo.loadAddressUnslid    = loadAddressUnslid;
        dylibTextInfo.textSegmentSize      = textSegmentSize;
        dylibTextInfo.path                 = installName;
        ::memcpy(dylibTextInfo.dylibUuid, dylibUUID, 16);
        dylibTextInfo.textSegmentOffset    = loadAddressUnslid - cacheUnslidBaseAddress;
        callback(&dylibTextInfo);
    });

    if ( sizeMapped != 0 )
        ::munmap((void*)sharedCache, sizeMapped);

    return 0;
}

int dyld_shared_cache_iterate_text(const uuid_t cacheUuid, void (^callback)(const dyld_shared_cache_dylib_text_info* info))
{
    log_apis("dyld_shared_cache_iterate_text()\n");

    const char* extraSearchDirs[] = { NULL };
    return dyld3::dyld_shared_cache_find_iterate_text(cacheUuid, extraSearchDirs, callback);
}
    
bool dyld_need_closure(const char* execPath, const char* dataContainerRootDir) {
    log_apis("dyld_need_closure(%s)\n", execPath);

    // We don't need to build a closure if the shared cache has it already
    const DyldSharedCache* sharedCache = (DyldSharedCache*)gAllImages.cacheLoadAddress();
    if ( sharedCache != nullptr ) {
        if ( sharedCache->findClosure(execPath) != nullptr )        // 查找必包的位置
            return false;
    }

    // this SPI changed. Originally the second path was to $TMPDIR, now it is $HOME
    // if called old way, adjust
    size_t rootDirLen = strlen(dataContainerRootDir);
    char homeFromTmp[PATH_MAX];
    if ( (rootDirLen > 5) && (strcmp(&dataContainerRootDir[rootDirLen-4], "/tmp") == 0) && (rootDirLen < PATH_MAX) ) {
        strlcpy(homeFromTmp, dataContainerRootDir, PATH_MAX);
        homeFromTmp[rootDirLen-4] = '\0';
        dataContainerRootDir = homeFromTmp;
    }

    // dummy up envp needed by buildClosureCachePath()
    char strBuf[PATH_MAX+8]; // room for HOME= and max path
    strcpy(strBuf, "HOME=");
    strlcat(strBuf, dataContainerRootDir, sizeof(strBuf));
    const char* envp[2];
    envp[0] = strBuf;
    envp[1] = nullptr;

    // 拼接启动必包的路径：在App的沙盒环境目录中 /private/var/mobile/Containers/Data/uuid/Library/Caches/com.apple.dyld/appname.closure
    char closurePath[PATH_MAX];
    if ( dyld3::closure::LaunchClosure::buildClosureCachePath(execPath, envp, false, closurePath) ) {
        struct stat statbuf;
        // if no file at location where closure would be stored, then need to build a closure
        // 校验在这个路径下是否文件
        return (dyld3::stat(closurePath, &statbuf) != 0);
    }

    // Not containerized so no point in building a closure.
    return false;
}

void _dyld_missing_symbol_abort()
{
    // We don't know the name of the lazy symbol that is missing.
    // dyld3 binds all such missing symbols to this one handler.
    // We need the crash log to contain the backtrace so someone can
    // figure out the symbol.

    auto allImageInfos = gAllImages.oldAllImageInfo();
    allImageInfos->errorKind           = DYLD_EXIT_REASON_SYMBOL_MISSING;
    allImageInfos->errorClientOfDylibPath   = "<unknown>";
    allImageInfos->errorTargetDylibPath     = "<unknown>";
    allImageInfos->errorSymbol              = "<unknown>";

    halt("missing lazy symbol called");
}

/* 根据selName看看能够通过必包的缓存（_objcSelectorHashTableImages）找到存储该字符串对应的Image以及在Image的偏移位置；有的话，返回存储的char *，没有返回null
 * 注意1: _objcSelectorHashTable存储数据的时机是：objc库的初始化方法objc_init里面会像dyld注册3个回调，
 *      在dyld库的注册方法里面，会从必包中获取sel数据存储到这里
 * 注意2: 在objc的初始化方法objc_init后面会调用read_images里面，会获取hi里面的sel，然后进行修复：
 *      会调用这里，根据name查询是否能获取到对应的sel
 */
const char* _dyld_get_objc_selector(const char* selName) {
    log_apis("dyld_get_objc_selector()\n");
    /* 根据selName看看能够通过必包的缓存（_objcSelectorHashTableImages）找到存储该字符串对应的Image以及在Image的偏移位置；有的话，返回存储的char *，没有返回null
     * 注意1: _objcSelectorHashTable存储数据的时机是：objc库的初始化方法objc_init里面会像dyld注册3个回调，
     *      在dyld库的注册方法里面，会从必包中获取sel数据存储到这里
     * 注意2: 在objc的初始化方法objc_init后面会调用read_images里面，会获取hi里面的sel，然后进行修复：
     *      会调用这里，根据name查询是否能获取到对应的sel
     */
    return gAllImages.getObjCSelector(selName);
}

// 去_objcClassHashTableImages（里面存放的应该是objc相关库的class）里查找className在哪个Image中，找到后，让cls调用回调
void _dyld_for_each_objc_class(const char* className,
                               void (^callback)(void* classPtr, bool isLoaded, bool* stop)) {
    log_apis("_dyld_for_each_objc_class()\n");
    gAllImages.forEachObjCClass(className, callback);
}

void _dyld_for_each_objc_protocol(const char* protocolName,
                                  void (^callback)(void* protocolPtr, bool isLoaded, bool* stop)) {
    log_apis("_dyld_for_each_objc_protocol()\n");
    gAllImages.forEachObjCProtocol(protocolName, callback);
}

void _dyld_register_driverkit_main(void (*mainFunc)())
{
    log_apis("_dyld_register_driverkit_main()\n");
    gAllImages.setDriverkitMain(mainFunc);
}

#if !TARGET_OS_DRIVERKIT
struct dyld_func {
    const char*  name;
    void*        implementation;
};

static const struct dyld_func dyld_funcs[] = {
    {"__dyld_dlsym",                    (void*)dlsym }, // needs to go through generic function to get caller address
    {"__dyld_dlopen",                   (void*)dlopen },// needs to go through generic function to get caller address
    {"__dyld_dladdr",                   (void*)dyld3::dladdr },
    {"__dyld_image_count",              (void*)dyld3::_dyld_image_count },
    {"__dyld_get_image_name",           (void*)dyld3::_dyld_get_image_name },
    {"__dyld_get_image_header",         (void*)dyld3::_dyld_get_image_header },
    {"__dyld_get_image_vmaddr_slide",   (void*)dyld3::_dyld_get_image_vmaddr_slide },
#if TARGET_OS_OSX
    // <rdar://problem/59265987> support old licenseware plug ins on macOS
    {"__dyld_lookup_and_bind",          (void*)dyld3::_dyld_lookup_and_bind },
#endif
};
#endif

int compatFuncLookup(const char* name, void** address)
{
#if !TARGET_OS_DRIVERKIT
    for (const dyld_func* p = dyld_funcs; p->name != NULL; ++p) {
        if ( strcmp(p->name, name) == 0 ) {
            *address = p->implementation;
            return true;
        }
    }
    *address = 0;
#endif
    return false;
}



} // namespace dyld3

